v24Read is the basic function to get one or more received data bytes out of the receive queue. If the queue is empty, the behavious of the function depends on the used open flags. Without any open flags, a empty receive queue leads to an error. If the flag V24_NON_BLOCK is used, the function will wait for the reception of character. The wait time is limited to the given timeout time. If this limit is exceeded, the function aborts waiting. If nothing is read, the returned value is 0, and the error code is set to V24_E_TIMEOUT. At this level it's no real error, so there is no error report for the debug output (see V24_DEBUG_ON in v24OpenPort).The parameter Buffer references a buffer that should hold the received characters. The parameter Len is the number of characters to read.
The function returns the number of character read. An error is indicated by a return vlaue of -1. Use v24QueryErrno to get the exact error code.
Possible error code are V24_OK, V24_E_NULL_POINTER, V24_E_ILLHANDLE, V24_E_TIMEOUT or V24_READ.
Note: the caller has to ensure, that Buffer can hold the Len characters.